/*
 * contrib/tablefunc/tablefunc.c
 *
 *
 * tablefunc
 *
 * Sample to demonstrate C functions which return setof scalar
 * and setof composite.
 * Joe Conway <mail@joeconway.com>
 * And contributors:
 * Nabil Sayegh <postgresql@e-trolley.de>
 *
 * Copyright (c) 2002-2012, PostgreSQL Global Development Group
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without a written agreement
 * is hereby granted, provided that the above copyright notice and this
 * paragraph and the following two paragraphs appear in all copies.
 *
 * IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
 * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
 * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 */
#include "postgres.h"
#include "knl/knl_variable.h"

#include <math.h>

#include "catalog/pg_type.h"
#include "funcapi.h"
#include "executor/spi.h"
#include "miscadmin.h"
#include "utils/builtins.h"

#include "tablefunc.h"

PG_MODULE_MAGIC;

static HTAB* load_categories_hash(char* cats_sql, MemoryContext per_query_ctx);
static Tuplestorestate* get_crosstab_tuplestore(
    char* sql, HTAB* crosstab_hash, TupleDesc tupdesc, MemoryContext per_query_ctx, bool randomAccess);
static void validateConnectbyTupleDesc(TupleDesc tupdesc, bool show_branch, bool show_serial);
static bool compatCrosstabTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
static bool compatConnectbyTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
static void get_normal_pair(float8* x1, float8* x2);
static Tuplestorestate* connectby(char* relname, char* key_fld, char* parent_key_fld, char* orderby_fld,
    char* branch_delim, char* start_with, int max_depth, bool show_branch, bool show_serial,
    MemoryContext per_query_ctx, bool randomAccess, AttInMetadata* attinmeta);
static Tuplestorestate* build_tuplestore_recursively(char* key_fld, char* parent_key_fld, char* relname,
    char* orderby_fld, char* branch_delim, char* start_with, char* branch, int level, int* serial, int max_depth,
    bool show_branch, bool show_serial, MemoryContext per_query_ctx, AttInMetadata* attinmeta,
    Tuplestorestate* tupstore);

typedef struct {
    float8 mean;      /* mean of the distribution */
    float8 stddev;    /* stddev of the distribution */
    float8 carry_val; /* hold second generated value */
    bool use_carry;   /* use second generated value */
} normal_rand_fctx;

#define xpfree(var_)        \
    do {                    \
        if (var_ != NULL) { \
            pfree(var_);    \
            var_ = NULL;    \
        }                   \
    } while (0)

#define xpstrdup(tgtvar_, srcvar_)      \
    do {                                \
        if (srcvar_)                    \
            tgtvar_ = pstrdup(srcvar_); \
        else                            \
            tgtvar_ = NULL;             \
    } while (0)

#define xstreq(tgtvar_, srcvar_)                 \
    (((tgtvar_ == NULL) && (srcvar_ == NULL)) || \
        ((tgtvar_ != NULL) && (srcvar_ != NULL) && (strcmp(tgtvar_, srcvar_) == 0)))

/* sign, 10 digits, '\0' */
#define INT32_STRLEN 12

/* stored info for a crosstab category */
typedef struct crosstab_cat_desc {
    char* catname; /* full category name */
    int attidx;    /* zero based */
} crosstab_cat_desc;

#define MAX_CATNAME_LEN NAMEDATALEN
#define INIT_CATS 64

#define crosstab_HashTableLookup(HASHTAB, CATNAME, CATDESC)                     \
    do {                                                                        \
        crosstab_HashEnt* hentry;                                               \
        char key[MAX_CATNAME_LEN] = {0};                                        \
        int rc = snprintf_s(key, MAX_CATNAME_LEN,                               \
                            MAX_CATNAME_LEN - 1, "%s", CATNAME);                \
        securec_check_ss(rc, "", "");                                           \        
        hentry = (crosstab_HashEnt*)hash_search(HASHTAB, key, HASH_FIND, NULL); \
        if (hentry)                                                             \
            CATDESC = hentry->catdesc;                                          \
        else                                                                    \
            CATDESC = NULL;                                                     \
    } while (0)

#define crosstab_HashTableInsert(HASHTAB, CATDESC)                                                  \
    do {                                                                                            \
        crosstab_HashEnt* hentry;                                                                   \
        bool found;                                                                                 \
        char key[MAX_CATNAME_LEN] = {0};                                                            \
        int rc = snprintf_s(key, MAX_CATNAME_LEN,                                                   \
                            MAX_CATNAME_LEN - 1, "%s", CATDESC->catname);                           \
        securec_check_ss(rc, "", "");                                           \        
        hentry = (crosstab_HashEnt*)hash_search(HASHTAB, key, HASH_ENTER, &found);                  \
        if (found)                                                                                  \
            ereport(ERROR, (errcode(ERRCODE_DUPLICATE_OBJECT), errmsg("duplicate category name"))); \
        hentry->catdesc = CATDESC;                                                                  \
    } while (0)

/* hash table */
typedef struct crosstab_hashent {
    char internal_catname[MAX_CATNAME_LEN];
    crosstab_cat_desc* catdesc;
} crosstab_HashEnt;

/*
 * normal_rand - return requested number of random values
 * with a Gaussian (Normal) distribution.
 *
 * inputs are int numvals, float8 mean, and float8 stddev
 * returns setof float8
 */
PG_FUNCTION_INFO_V1(normal_rand);
Datum normal_rand(PG_FUNCTION_ARGS)
{
    FuncCallContext* funcctx = NULL;
    int call_cntr;
    int max_calls;
    normal_rand_fctx* fctx = NULL;
    float8 mean;
    float8 stddev;
    float8 carry_val;
    bool use_carry = false;
    MemoryContext oldcontext;

    /* stuff done only on the first call of the function */
    if (SRF_IS_FIRSTCALL()) {
        /* create a function context for cross-call persistence */
        funcctx = SRF_FIRSTCALL_INIT();

        /*
         * switch to memory context appropriate for multiple function calls
         */
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        /* total number of tuples to be returned */
        funcctx->max_calls = PG_GETARG_UINT32(0);

        /* allocate memory for user context */
        fctx = (normal_rand_fctx*)palloc(sizeof(normal_rand_fctx));

        /*
         * Use fctx to keep track of upper and lower bounds from call to call.
         * It will also be used to carry over the spare value we get from the
         * Box-Muller algorithm so that we only actually calculate a new value
         * every other call.
         */
        fctx->mean = PG_GETARG_FLOAT8(1);
        fctx->stddev = PG_GETARG_FLOAT8(2);
        fctx->carry_val = 0;
        fctx->use_carry = false;

        funcctx->user_fctx = fctx;

        MemoryContextSwitchTo(oldcontext);
    }

    /* stuff done on every call of the function */
    funcctx = SRF_PERCALL_SETUP();

    call_cntr = funcctx->call_cntr;
    max_calls = funcctx->max_calls;
    fctx = (normal_rand_fctx*)funcctx->user_fctx;
    mean = fctx->mean;
    stddev = fctx->stddev;
    carry_val = fctx->carry_val;
    use_carry = fctx->use_carry;

    if (call_cntr < max_calls) /* do when there is more left to send */
    {
        float8 result;

        if (use_carry) {
            /*
             * reset use_carry and use second value obtained on last pass
             */
            fctx->use_carry = false;
            result = carry_val;
        } else {
            float8 normval_1;
            float8 normval_2;

            /* Get the next two normal values */
            get_normal_pair(&normval_1, &normval_2);

            /* use the first */
            result = mean + (stddev * normval_1);

            /* and save the second */
            fctx->carry_val = mean + (stddev * normval_2);
            fctx->use_carry = true;
        }

        /* send the result */
        SRF_RETURN_NEXT(funcctx, Float8GetDatum(result));
    } else
        /* do when there is no more left */
        SRF_RETURN_DONE(funcctx);
}

/*
 * get_normal_pair()
 * Assigns normally distributed (Gaussian) values to a pair of provided
 * parameters, with mean 0, standard deviation 1.
 *
 * This routine implements Algorithm P (Polar method for normal deviates)
 * from Knuth's _The_Art_of_Computer_Programming_, Volume 2, 3rd ed., pages
 * 122-126. Knuth cites his source as "The polar method", G. E. P. Box, M. E.
 * Muller, and G. Marsaglia, _Annals_Math,_Stat._ 29 (1958), 610-611.
 *
 */
static void get_normal_pair(float8* x1, float8* x2)
{
    float8 u1, u2, v1, v2, s;

    do {
        u1 = (float8)random() / (float8)MAX_RANDOM_VALUE;
        u2 = (float8)random() / (float8)MAX_RANDOM_VALUE;

        v1 = (2.0 * u1) - 1.0;
        v2 = (2.0 * u2) - 1.0;

        s = v1 * v1 + v2 * v2;
    } while (s >= 1.0);

    if (s == 0) {
        *x1 = 0;
        *x2 = 0;
    } else {
        s = sqrt((-2.0 * log(s)) / s);
        *x1 = v1 * s;
        *x2 = v2 * s;
    }
}

/*
 * crosstab - create a crosstab of rowids and values columns from a
 * SQL statement returning one rowid column, one category column,
 * and one value column.
 *
 * e.g. given sql which produces:
 *
 *			rowid	cat		value
 *			------+-------+-------
 *			row1	cat1	val1
 *			row1	cat2	val2
 *			row1	cat3	val3
 *			row1	cat4	val4
 *			row2	cat1	val5
 *			row2	cat2	val6
 *			row2	cat3	val7
 *			row2	cat4	val8
 *
 * crosstab returns:
 *					<===== values columns =====>
 *			rowid	cat1	cat2	cat3	cat4
 *			------+-------+-------+-------+-------
 *			row1	val1	val2	val3	val4
 *			row2	val5	val6	val7	val8
 *
 * NOTES:
 * 1. SQL result must be ordered by 1,2.
 * 2. The number of values columns depends on the tuple description
 *	  of the function's declared return type.  The return type's columns
 *	  must match the datatypes of the SQL query's result.  The datatype
 *	  of the category column can be anything, however.
 * 3. Missing values (i.e. not enough adjacent rows of same rowid to
 *	  fill the number of result values columns) are filled in with nulls.
 * 4. Extra values (i.e. too many adjacent rows of same rowid to fill
 *	  the number of result values columns) are skipped.
 * 5. Rows with all nulls in the values columns are skipped.
 */
PG_FUNCTION_INFO_V1(crosstab);
Datum crosstab(PG_FUNCTION_ARGS)
{
    char* sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
    ReturnSetInfo* rsinfo = (ReturnSetInfo*)fcinfo->resultinfo;
    Tuplestorestate* tupstore = NULL;
    TupleDesc tupdesc;
    int call_cntr;
    int max_calls;
    AttInMetadata* attinmeta = NULL;
    SPITupleTable* spi_tuptable = NULL;
    TupleDesc spi_tupdesc;
    bool firstpass = false;
    char* lastrowid = NULL;
    int i;
    int num_categories;
    MemoryContext per_query_ctx;
    MemoryContext oldcontext;
    int ret;
    int proc;

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize))
        ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("materialize mode required, but it is not "
                       "allowed in this context")));

    per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;

    /* Connect to SPI manager */
    if ((ret = SPI_connect()) < 0)
        /* internal error */
        elog(ERROR, "crosstab: SPI_connect returned %d", ret);

    /* Retrieve the desired rows */
    ret = SPI_execute(sql, true, 0);
    proc = SPI_processed;

    /* If no qualifying tuples, fall out early */
    if (ret != SPI_OK_SELECT || proc <= 0) {
        SPI_finish();
        rsinfo->isDone = ExprEndResult;
        PG_RETURN_NULL();
    }

    spi_tuptable = SPI_tuptable;
    spi_tupdesc = spi_tuptable->tupdesc;

    /*----------
     * The provided SQL query must always return three columns.
     *
     * 1. rowname
     *	the label or identifier for each row in the final result
     * 2. category
     *	the label or identifier for each column in the final result
     * 3. values
     *	the value for each column in the final result
     *----------
     */
    if (spi_tupdesc->natts != 3)
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("invalid source data SQL statement"),
                errdetail("The provided SQL must return 3 "
                          "columns: rowid, category, and values.")));

    /* get a tuple descriptor for our result type */
    switch (get_call_result_type(fcinfo, NULL, &tupdesc)) {
        case TYPEFUNC_COMPOSITE:
            /* success */
            break;
        case TYPEFUNC_RECORD:
            /* failed to determine actual type of RECORD */
            ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                    errmsg("function returning record called in context "
                           "that cannot accept type record")));
            break;
        default:
            /* result type isn't composite */
            elog(ERROR, "return type must be a row type");
            break;
    }

    /*
     * Check that return tupdesc is compatible with the data we got from SPI,
     * at least based on number and type of attributes
     */
    if (!compatCrosstabTupleDescs(tupdesc, spi_tupdesc))
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("return and sql tuple descriptions are "
                       "incompatible")));

    /*
     * switch to long-lived memory context
     */
    oldcontext = MemoryContextSwitchTo(per_query_ctx);

    /* make sure we have a persistent copy of the result tupdesc */
    tupdesc = CreateTupleDescCopy(tupdesc);

    /* initialize our tuplestore in long-lived context */
    tupstore =
        tuplestore_begin_heap(rsinfo->allowedModes & SFRM_Materialize_Random, false, u_sess->attr.attr_memory.work_mem);

    MemoryContextSwitchTo(oldcontext);

    /*
     * Generate attribute metadata needed later to produce tuples from raw C
     * strings
     */
    attinmeta = TupleDescGetAttInMetadata(tupdesc);

    /* total number of tuples to be examined */
    max_calls = proc;

    /* the return tuple always must have 1 rowid + num_categories columns */
    num_categories = tupdesc->natts - 1;

    firstpass = true;
    lastrowid = NULL;

    for (call_cntr = 0; call_cntr < max_calls; call_cntr++) {
        bool skip_tuple = false;
        char** values;

        /* allocate and zero space */
        values = (char**)palloc0((1 + num_categories) * sizeof(char*));

        /*
         * now loop through the sql results and assign each value in sequence
         * to the next category
         */
        for (i = 0; i < num_categories; i++) {
            HeapTuple spi_tuple;
            char* rowid = NULL;

            /* see if we've gone too far already */
            if (call_cntr >= max_calls)
                break;

            /* get the next sql result tuple */
            spi_tuple = spi_tuptable->vals[call_cntr];

            /* get the rowid from the current sql result tuple */
            rowid = SPI_getvalue(spi_tuple, spi_tupdesc, 1);

            /*
             * If this is the first pass through the values for this rowid,
             * set the first column to rowid
             */
            if (i == 0) {
                xpstrdup(values[0], rowid);

                /*
                 * Check to see if the rowid is the same as that of the last
                 * tuple sent -- if so, skip this tuple entirely
                 */
                if (!firstpass && xstreq(lastrowid, rowid)) {
                    xpfree(rowid);
                    skip_tuple = true;
                    break;
                }
            }

            /*
             * If rowid hasn't changed on us, continue building the output
             * tuple.
             */
            if (xstreq(rowid, values[0])) {
                /*
                 * Get the next category item value, which is always attribute
                 * number three.
                 *
                 * Be careful to assign the value to the array index based on
                 * which category we are presently processing.
                 */
                values[1 + i] = SPI_getvalue(spi_tuple, spi_tupdesc, 3);

                /*
                 * increment the counter since we consume a row for each
                 * category, but not for last pass because the outer loop will
                 * do that for us
                 */
                if (i < (num_categories - 1))
                    call_cntr++;
                xpfree(rowid);
            } else {
                /*
                 * We'll fill in NULLs for the missing values, but we need to
                 * decrement the counter since this sql result row doesn't
                 * belong to the current output tuple.
                 */
                call_cntr--;
                xpfree(rowid);
                break;
            }
        }

        if (!skip_tuple) {
            HeapTuple tuple;

            /* build the tuple and store it */
            tuple = BuildTupleFromCStrings(attinmeta, values);
            tuplestore_puttuple(tupstore, tuple);
            heap_freetuple(tuple);
        }

        /* Remember current rowid */
        xpfree(lastrowid);
        xpstrdup(lastrowid, values[0]);
        firstpass = false;

        /* Clean up */
        for (i = 0; i < num_categories + 1; i++)
            if (values[i] != NULL)
                pfree(values[i]);
        pfree(values);
    }

    /* let the caller know we're sending back a tuplestore */
    rsinfo->returnMode = SFRM_Materialize;
    rsinfo->setResult = tupstore;
    rsinfo->setDesc = tupdesc;

    /* release SPI related resources (and return to caller's context) */
    SPI_finish();

    return (Datum)0;
}

/*
 * crosstab_hash - reimplement crosstab as materialized function and
 * properly deal with missing values (i.e. don't pack remaining
 * values to the left)
 *
 * crosstab - create a crosstab of rowids and values columns from a
 * SQL statement returning one rowid column, one category column,
 * and one value column.
 *
 * e.g. given sql which produces:
 *
 *			rowid	cat		value
 *			------+-------+-------
 *			row1	cat1	val1
 *			row1	cat2	val2
 *			row1	cat4	val4
 *			row2	cat1	val5
 *			row2	cat2	val6
 *			row2	cat3	val7
 *			row2	cat4	val8
 *
 * crosstab returns:
 *					<===== values columns =====>
 *			rowid	cat1	cat2	cat3	cat4
 *			------+-------+-------+-------+-------
 *			row1	val1	val2	null	val4
 *			row2	val5	val6	val7	val8
 *
 * NOTES:
 * 1. SQL result must be ordered by 1.
 * 2. The number of values columns depends on the tuple description
 *	  of the function's declared return type.
 * 3. Missing values (i.e. missing category) are filled in with nulls.
 * 4. Extra values (i.e. not in category results) are skipped.
 */
PG_FUNCTION_INFO_V1(crosstab_hash);
Datum crosstab_hash(PG_FUNCTION_ARGS)
{
    char* sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
    char* cats_sql = text_to_cstring(PG_GETARG_TEXT_PP(1));
    ReturnSetInfo* rsinfo = (ReturnSetInfo*)fcinfo->resultinfo;
    TupleDesc tupdesc;
    MemoryContext per_query_ctx;
    MemoryContext oldcontext;
    HTAB* crosstab_hash = NULL;

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize) || rsinfo->expectedDesc == NULL)
        ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("materialize mode required, but it is not "
                       "allowed in this context")));

    per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
    oldcontext = MemoryContextSwitchTo(per_query_ctx);

    /* get the requested return tuple description */
    tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);

    /*
     * Check to make sure we have a reasonable tuple descriptor
     *
     * Note we will attempt to coerce the values into whatever the return
     * attribute type is and depend on the "in" function to complain if
     * needed.
     */
    if (tupdesc->natts < 2)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("query-specified return tuple and "
                       "crosstab function are not compatible")));

    /* load up the categories hash table */
    crosstab_hash = load_categories_hash(cats_sql, per_query_ctx);

    /* let the caller know we're sending back a tuplestore */
    rsinfo->returnMode = SFRM_Materialize;

    /* now go build it */
    rsinfo->setResult = get_crosstab_tuplestore(
        sql, crosstab_hash, tupdesc, per_query_ctx, rsinfo->allowedModes & SFRM_Materialize_Random);

    /*
     * SFRM_Materialize mode expects us to return a NULL Datum. The actual
     * tuples are in our tuplestore and passed back through rsinfo->setResult.
     * rsinfo->setDesc is set to the tuple description that we actually used
     * to build our tuples with, so the caller can verify we did what it was
     * expecting.
     */
    rsinfo->setDesc = tupdesc;
    MemoryContextSwitchTo(oldcontext);

    return (Datum)0;
}

/*
 * load up the categories hash table
 */
static HTAB* load_categories_hash(char* cats_sql, MemoryContext per_query_ctx)
{
    HTAB* crosstab_hash = NULL;
    HASHCTL ctl;
    int ret;
    int proc;
    MemoryContext SPIcontext;

    /* initialize the category hash table */
    MemSet(&ctl, 0, sizeof(ctl));
    ctl.keysize = MAX_CATNAME_LEN;
    ctl.entrysize = sizeof(crosstab_HashEnt);
    ctl.hcxt = per_query_ctx;

    /*
     * use INIT_CATS, defined above as a guess of how many hash table entries
     * to create, initially
     */
    crosstab_hash = hash_create("crosstab hash", INIT_CATS, &ctl, HASH_ELEM | HASH_CONTEXT);

    /* Connect to SPI manager */
    if ((ret = SPI_connect()) < 0)
        /* internal error */
        elog(ERROR, "load_categories_hash: SPI_connect returned %d", ret);

    /* Retrieve the category name rows */
    ret = SPI_execute(cats_sql, true, 0);
    proc = SPI_processed;

    /* Check for qualifying tuples */
    if ((ret == SPI_OK_SELECT) && (proc > 0)) {
        SPITupleTable* spi_tuptable = SPI_tuptable;
        TupleDesc spi_tupdesc = spi_tuptable->tupdesc;
        int i;

        /*
         * The provided categories SQL query must always return one column:
         * category - the label or identifier for each column
         */
        if (spi_tupdesc->natts != 1)
            ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("provided \"categories\" SQL must "
                           "return 1 column of at least one row")));

        for (i = 0; i < proc; i++) {
            crosstab_cat_desc* catdesc = NULL;
            char* catname = NULL;
            HeapTuple spi_tuple;

            /* get the next sql result tuple */
            spi_tuple = spi_tuptable->vals[i];

            /* get the category from the current sql result tuple */
            catname = SPI_getvalue(spi_tuple, spi_tupdesc, 1);

            SPIcontext = MemoryContextSwitchTo(per_query_ctx);

            catdesc = (crosstab_cat_desc*)palloc(sizeof(crosstab_cat_desc));
            catdesc->catname = catname;
            catdesc->attidx = i;

            /* Add the proc description block to the hashtable */
            crosstab_HashTableInsert(crosstab_hash, catdesc);

            MemoryContextSwitchTo(SPIcontext);
        }
    }
    if (SPI_finish() != SPI_OK_FINISH)
        /* internal error */
        elog(ERROR, "load_categories_hash: SPI_finish() failed");

    return crosstab_hash;
}

/*
 * create and populate the crosstab tuplestore using the provided source query
 */
static Tuplestorestate* get_crosstab_tuplestore(
    char* sql, HTAB* crosstab_hash, TupleDesc tupdesc, MemoryContext per_query_ctx, bool randomAccess)
{
    Tuplestorestate* tupstore = NULL;
    int num_categories = hash_get_num_entries(crosstab_hash);
    AttInMetadata* attinmeta = TupleDescGetAttInMetadata(tupdesc);
    char** values;
    HeapTuple tuple;
    int ret;
    int proc;

    /* initialize our tuplestore (while still in query context!) */
    tupstore = tuplestore_begin_heap(randomAccess, false, u_sess->attr.attr_memory.work_mem);

    /* Connect to SPI manager */
    if ((ret = SPI_connect()) < 0)
        /* internal error */
        elog(ERROR, "get_crosstab_tuplestore: SPI_connect returned %d", ret);

    /* Now retrieve the crosstab source rows */
    ret = SPI_execute(sql, true, 0);
    proc = SPI_processed;

    /* Check for qualifying tuples */
    if ((ret == SPI_OK_SELECT) && (proc > 0)) {
        SPITupleTable* spi_tuptable = SPI_tuptable;
        TupleDesc spi_tupdesc = spi_tuptable->tupdesc;
        int ncols = spi_tupdesc->natts;
        char* rowid = NULL;
        char* lastrowid = NULL;
        bool firstpass = true;
        int i, j;
        int result_ncols;

        if (num_categories == 0) {
            /* no qualifying category tuples */
            ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("provided \"categories\" SQL must "
                           "return 1 column of at least one row")));
        }

        /*
         * The provided SQL query must always return at least three columns:
         *
         * 1. rowname	the label for each row - column 1 in the final result
         * 2. category	the label for each value-column in the final result 3.
         * value	 the values used to populate the value-columns
         *
         * If there are more than three columns, the last two are taken as
         * "category" and "values". The first column is taken as "rowname".
         * Additional columns (2 thru N-2) are assumed the same for the same
         * "rowname", and are copied into the result tuple from the first time
         * we encounter a particular rowname.
         */
        if (ncols < 3)
            ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                    errmsg("invalid source data SQL statement"),
                    errdetail("The provided SQL must return 3 "
                              " columns; rowid, category, and values.")));

        result_ncols = (ncols - 2) + num_categories;

        /* Recheck to make sure we tuple descriptor still looks reasonable */
        if (tupdesc->natts != result_ncols)
            ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("invalid return type"),
                    errdetail("Query-specified return "
                              "tuple has %d columns but crosstab "
                              "returns %d.",
                        tupdesc->natts,
                        result_ncols)));

        /* allocate space */
        values = (char**)palloc(result_ncols * sizeof(char*));

        /* and make sure it's clear */
        memset(values, '\0', result_ncols * sizeof(char*));

        for (i = 0; i < proc; i++) {
            HeapTuple spi_tuple;
            crosstab_cat_desc* catdesc = NULL;
            char* catname = NULL;

            /* get the next sql result tuple */
            spi_tuple = spi_tuptable->vals[i];

            /* get the rowid from the current sql result tuple */
            rowid = SPI_getvalue(spi_tuple, spi_tupdesc, 1);

            /*
             * if we're on a new output row, grab the column values up to
             * column N-2 now
             */
            if (firstpass || !xstreq(lastrowid, rowid)) {
                /*
                 * a new row means we need to flush the old one first, unless
                 * we're on the very first row
                 */
                if (!firstpass) {
                    /* rowid changed, flush the previous output row */
                    tuple = BuildTupleFromCStrings(attinmeta, values);

                    tuplestore_puttuple(tupstore, tuple);

                    for (j = 0; j < result_ncols; j++)
                        xpfree(values[j]);
                }

                values[0] = rowid;
                for (j = 1; j < ncols - 2; j++)
                    values[j] = SPI_getvalue(spi_tuple, spi_tupdesc, j + 1);

                /* we're no longer on the first pass */
                firstpass = false;
            }

            /* look up the category and fill in the appropriate column */
            catname = SPI_getvalue(spi_tuple, spi_tupdesc, ncols - 1);

            if (catname != NULL) {
                crosstab_HashTableLookup(crosstab_hash, catname, catdesc);

                if (catdesc)
                    values[catdesc->attidx + ncols - 2] = SPI_getvalue(spi_tuple, spi_tupdesc, ncols);
            }

            xpfree(lastrowid);
            xpstrdup(lastrowid, rowid);
        }

        /* flush the last output row */
        tuple = BuildTupleFromCStrings(attinmeta, values);

        tuplestore_puttuple(tupstore, tuple);
    }

    if (SPI_finish() != SPI_OK_FINISH)
        /* internal error */
        elog(ERROR, "get_crosstab_tuplestore: SPI_finish() failed");

    tuplestore_donestoring(tupstore);

    return tupstore;
}

/*
 * connectby_text - produce a result set from a hierarchical (parent/child)
 * table.
 *
 * e.g. given table foo:
 *
 *			keyid	parent_keyid pos
 *			------+------------+--
 *			row1	NULL		 0
 *			row2	row1		 0
 *			row3	row1		 0
 *			row4	row2		 1
 *			row5	row2		 0
 *			row6	row4		 0
 *			row7	row3		 0
 *			row8	row6		 0
 *			row9	row5		 0
 *
 *
 * connectby(text relname, text keyid_fld, text parent_keyid_fld
 *			  [, text orderby_fld], text start_with, int max_depth
 *			  [, text branch_delim])
 * connectby('foo', 'keyid', 'parent_keyid', 'pos', 'row2', 0, '~') returns:
 *
 *		keyid	parent_id	level	 branch				serial
 *		------+-----------+--------+-----------------------
 *		row2	NULL		  0		  row2				  1
 *		row5	row2		  1		  row2~row5			  2
 *		row9	row5		  2		  row2~row5~row9	  3
 *		row4	row2		  1		  row2~row4			  4
 *		row6	row4		  2		  row2~row4~row6	  5
 *		row8	row6		  3		  row2~row4~row6~row8 6
 *
 */
PG_FUNCTION_INFO_V1(connectby_text);

#define CONNECTBY_NCOLS 4
#define CONNECTBY_NCOLS_NOBRANCH 3

Datum connectby_text(PG_FUNCTION_ARGS)
{
    char* relname = text_to_cstring(PG_GETARG_TEXT_PP(0));
    char* key_fld = text_to_cstring(PG_GETARG_TEXT_PP(1));
    char* parent_key_fld = text_to_cstring(PG_GETARG_TEXT_PP(2));
    char* start_with = text_to_cstring(PG_GETARG_TEXT_PP(3));
    int max_depth = PG_GETARG_INT32(4);
    char* branch_delim = NULL;
    bool show_branch = false;
    bool show_serial = false;
    ReturnSetInfo* rsinfo = (ReturnSetInfo*)fcinfo->resultinfo;
    TupleDesc tupdesc;
    AttInMetadata* attinmeta = NULL;
    MemoryContext per_query_ctx;
    MemoryContext oldcontext;

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize) || rsinfo->expectedDesc == NULL)
        ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("materialize mode required, but it is not "
                       "allowed in this context")));

    if (fcinfo->nargs == 6) {
        branch_delim = text_to_cstring(PG_GETARG_TEXT_PP(5));
        show_branch = true;
    } else
        /* default is no show, tilde for the delimiter */
        branch_delim = pstrdup("~");

    per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
    oldcontext = MemoryContextSwitchTo(per_query_ctx);

    /* get the requested return tuple description */
    tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);

    /* does it meet our needs */
    validateConnectbyTupleDesc(tupdesc, show_branch, show_serial);

    /* OK, use it then */
    attinmeta = TupleDescGetAttInMetadata(tupdesc);

    /* OK, go to work */
    rsinfo->returnMode = SFRM_Materialize;
    rsinfo->setResult = connectby(relname,
        key_fld,
        parent_key_fld,
        NULL,
        branch_delim,
        start_with,
        max_depth,
        show_branch,
        show_serial,
        per_query_ctx,
        rsinfo->allowedModes & SFRM_Materialize_Random,
        attinmeta);
    rsinfo->setDesc = tupdesc;

    MemoryContextSwitchTo(oldcontext);

    /*
     * SFRM_Materialize mode expects us to return a NULL Datum. The actual
     * tuples are in our tuplestore and passed back through rsinfo->setResult.
     * rsinfo->setDesc is set to the tuple description that we actually used
     * to build our tuples with, so the caller can verify we did what it was
     * expecting.
     */
    return (Datum)0;
}

PG_FUNCTION_INFO_V1(connectby_text_serial);
Datum connectby_text_serial(PG_FUNCTION_ARGS)
{
    char* relname = text_to_cstring(PG_GETARG_TEXT_PP(0));
    char* key_fld = text_to_cstring(PG_GETARG_TEXT_PP(1));
    char* parent_key_fld = text_to_cstring(PG_GETARG_TEXT_PP(2));
    char* orderby_fld = text_to_cstring(PG_GETARG_TEXT_PP(3));
    char* start_with = text_to_cstring(PG_GETARG_TEXT_PP(4));
    int max_depth = PG_GETARG_INT32(5);
    char* branch_delim = NULL;
    bool show_branch = false;
    bool show_serial = true;
    ReturnSetInfo* rsinfo = (ReturnSetInfo*)fcinfo->resultinfo;
    TupleDesc tupdesc;
    AttInMetadata* attinmeta = NULL;
    MemoryContext per_query_ctx;
    MemoryContext oldcontext;

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize) || rsinfo->expectedDesc == NULL)
        ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("materialize mode required, but it is not "
                       "allowed in this context")));

    if (fcinfo->nargs == 7) {
        branch_delim = text_to_cstring(PG_GETARG_TEXT_PP(6));
        show_branch = true;
    } else
        /* default is no show, tilde for the delimiter */
        branch_delim = pstrdup("~");

    per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
    oldcontext = MemoryContextSwitchTo(per_query_ctx);

    /* get the requested return tuple description */
    tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);

    /* does it meet our needs */
    validateConnectbyTupleDesc(tupdesc, show_branch, show_serial);

    /* OK, use it then */
    attinmeta = TupleDescGetAttInMetadata(tupdesc);

    /* OK, go to work */
    rsinfo->returnMode = SFRM_Materialize;
    rsinfo->setResult = connectby(relname,
        key_fld,
        parent_key_fld,
        orderby_fld,
        branch_delim,
        start_with,
        max_depth,
        show_branch,
        show_serial,
        per_query_ctx,
        rsinfo->allowedModes & SFRM_Materialize_Random,
        attinmeta);
    rsinfo->setDesc = tupdesc;

    MemoryContextSwitchTo(oldcontext);

    /*
     * SFRM_Materialize mode expects us to return a NULL Datum. The actual
     * tuples are in our tuplestore and passed back through rsinfo->setResult.
     * rsinfo->setDesc is set to the tuple description that we actually used
     * to build our tuples with, so the caller can verify we did what it was
     * expecting.
     */
    return (Datum)0;
}

/*
 * connectby - does the real work for connectby_text()
 */
static Tuplestorestate* connectby(char* relname, char* key_fld, char* parent_key_fld, char* orderby_fld,
    char* branch_delim, char* start_with, int max_depth, bool show_branch, bool show_serial,
    MemoryContext per_query_ctx, bool randomAccess, AttInMetadata* attinmeta)
{
    Tuplestorestate* tupstore = NULL;
    int ret;
    MemoryContext oldcontext;

    int serial = 1;

    /* Connect to SPI manager */
    if ((ret = SPI_connect()) < 0)
        /* internal error */
        elog(ERROR, "connectby: SPI_connect returned %d", ret);

    /* switch to longer term context to create the tuple store */
    oldcontext = MemoryContextSwitchTo(per_query_ctx);

    /* initialize our tuplestore */
    tupstore = tuplestore_begin_heap(randomAccess, false, u_sess->attr.attr_memory.work_mem);

    MemoryContextSwitchTo(oldcontext);

    /* now go get the whole tree */
    tupstore = build_tuplestore_recursively(key_fld,
        parent_key_fld,
        relname,
        orderby_fld,
        branch_delim,
        start_with,
        start_with, /* current_branch */
        0,          /* initial level is 0 */
        &serial,    /* initial serial is 1 */
        max_depth,
        show_branch,
        show_serial,
        per_query_ctx,
        attinmeta,
        tupstore);

    SPI_finish();

    return tupstore;
}

static Tuplestorestate* build_tuplestore_recursively(char* key_fld, char* parent_key_fld, char* relname,
    char* orderby_fld, char* branch_delim, char* start_with, char* branch, int level, int* serial, int max_depth,
    bool show_branch, bool show_serial, MemoryContext per_query_ctx, AttInMetadata* attinmeta,
    Tuplestorestate* tupstore)
{
    TupleDesc tupdesc = attinmeta->tupdesc;
    int ret;
    int proc;
    int serial_column;
    StringInfoData sql;
    char** values;
    char* current_key = NULL;
    char* current_key_parent = NULL;
    char current_level[INT32_STRLEN];
    char serial_str[INT32_STRLEN];
    char* current_branch = NULL;
    HeapTuple tuple;
    int rc = 0;

    if (max_depth > 0 && level > max_depth)
        return tupstore;

    initStringInfo(&sql);

    /* Build initial sql statement */
    if (!show_serial) {
        appendStringInfo(&sql,
            "SELECT %s, %s FROM %s WHERE %s = %s AND %s IS NOT NULL AND %s <> %s",
            key_fld,
            parent_key_fld,
            relname,
            parent_key_fld,
            quote_literal_cstr(start_with),
            key_fld,
            key_fld,
            parent_key_fld);
        serial_column = 0;
    } else {
        appendStringInfo(&sql,
            "SELECT %s, %s FROM %s WHERE %s = %s AND %s IS NOT NULL AND %s <> %s ORDER BY %s",
            key_fld,
            parent_key_fld,
            relname,
            parent_key_fld,
            quote_literal_cstr(start_with),
            key_fld,
            key_fld,
            parent_key_fld,
            orderby_fld);
        serial_column = 1;
    }

    if (show_branch)
        values = (char**)palloc((CONNECTBY_NCOLS + serial_column) * sizeof(char*));
    else
        values = (char**)palloc((CONNECTBY_NCOLS_NOBRANCH + serial_column) * sizeof(char*));

    /* First time through, do a little setup */
    if (level == 0) {
        /* root value is the one we initially start with */
        values[0] = start_with;

        /* root value has no parent */
        values[1] = NULL;

        /* root level is 0 */
        rc = sprintf_s(current_level, INT32_STRLEN, "%d", level);
        secure_check_ss(rc, "", "");
        values[2] = current_level;

        /* root branch is just starting root value */
        if (show_branch)
            values[3] = start_with;

        /* root starts the serial with 1 */
        if (show_serial) {
            rc = sprintf_s(serial_str, INT32_STRLEN, "%d", (*serial)++);
            secure_check_ss(rc, "", "");
            if (show_branch)
                values[4] = serial_str;
            else
                values[3] = serial_str;
        }

        /* construct the tuple */
        tuple = BuildTupleFromCStrings(attinmeta, values);

        /* now store it */
        tuplestore_puttuple(tupstore, tuple);

        /* increment level */
        level++;
    }

    /* Retrieve the desired rows */
    ret = SPI_execute(sql.data, true, 0);
    proc = SPI_processed;

    /* Check for qualifying tuples */
    if ((ret == SPI_OK_SELECT) && (proc > 0)) {
        HeapTuple spi_tuple;
        SPITupleTable* tuptable = SPI_tuptable;
        TupleDesc spi_tupdesc = tuptable->tupdesc;
        int i;
        StringInfoData branchstr;
        StringInfoData chk_branchstr;
        StringInfoData chk_current_key;

        /* First time through, do a little more setup */
        if (level == 0) {
            /*
             * Check that return tupdesc is compatible with the one we got
             * from the query, but only at level 0 -- no need to check more
             * than once
             */

            if (!compatConnectbyTupleDescs(tupdesc, spi_tupdesc))
                ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                        errmsg("invalid return type"),
                        errdetail("Return and SQL tuple descriptions are "
                                  "incompatible.")));
        }

        initStringInfo(&branchstr);
        initStringInfo(&chk_branchstr);
        initStringInfo(&chk_current_key);

        for (i = 0; i < proc; i++) {
            /* initialize branch for this pass */
            appendStringInfo(&branchstr, "%s", branch);
            appendStringInfo(&chk_branchstr, "%s%s%s", branch_delim, branch, branch_delim);

            /* get the next sql result tuple */
            spi_tuple = tuptable->vals[i];

            /* get the current key and parent */
            current_key = SPI_getvalue(spi_tuple, spi_tupdesc, 1);
            appendStringInfo(&chk_current_key, "%s%s%s", branch_delim, current_key, branch_delim);
            current_key_parent = pstrdup(SPI_getvalue(spi_tuple, spi_tupdesc, 2));

            /* get the current level */
            rc = sprintf_s(current_level, INT32_STRLEN, "%d", level);
            secure_check_ss(rc, "", "");

            /* check to see if this key is also an ancestor */
            if (strstr(chk_branchstr.data, chk_current_key.data))
                elog(ERROR, "infinite recursion detected");

            /* OK, extend the branch */
            appendStringInfo(&branchstr, "%s%s", branch_delim, current_key);
            current_branch = branchstr.data;

            /* build a tuple */
            values[0] = pstrdup(current_key);
            values[1] = current_key_parent;
            values[2] = current_level;
            if (show_branch)
                values[3] = current_branch;
            if (show_serial) {
                rc = sprintf_s(serial_str, INT32_STRLEN, "%d", (*serial)++);
                secure_check_ss(rc, "", "");
                if (show_branch)
                    values[4] = serial_str;
                else
                    values[3] = serial_str;
            }

            tuple = BuildTupleFromCStrings(attinmeta, values);

            xpfree(current_key);
            xpfree(current_key_parent);

            /* store the tuple for later use */
            tuplestore_puttuple(tupstore, tuple);

            heap_freetuple(tuple);

            /* recurse using current_key_parent as the new start_with */
            tupstore = build_tuplestore_recursively(key_fld,
                parent_key_fld,
                relname,
                orderby_fld,
                branch_delim,
                values[0],
                current_branch,
                level + 1,
                serial,
                max_depth,
                show_branch,
                show_serial,
                per_query_ctx,
                attinmeta,
                tupstore);

            /* reset branch for next pass */
            resetStringInfo(&branchstr);
            resetStringInfo(&chk_branchstr);
            resetStringInfo(&chk_current_key);
        }

        xpfree(branchstr.data);
        xpfree(chk_branchstr.data);
        xpfree(chk_current_key.data);
    }

    return tupstore;
}

/*
 * Check expected (query runtime) tupdesc suitable for Connectby
 */
static void validateConnectbyTupleDesc(TupleDesc tupdesc, bool show_branch, bool show_serial)
{
    int serial_column = 0;

    if (show_serial)
        serial_column = 1;

    /* are there the correct number of columns */
    if (show_branch) {
        if (tupdesc->natts != (CONNECTBY_NCOLS + serial_column))
            ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("invalid return type"),
                    errdetail("Query-specified return tuple has "
                              "wrong number of columns.")));
    } else {
        if (tupdesc->natts != CONNECTBY_NCOLS_NOBRANCH + serial_column)
            ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("invalid return type"),
                    errdetail("Query-specified return tuple has "
                              "wrong number of columns.")));
    }

    /* check that the types of the first two columns match */
    if (tupdesc->attrs[0].atttypid != tupdesc->attrs[1].atttypid)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("invalid return type"),
                errdetail("First two columns must be the same type.")));

    /* check that the type of the third column is INT4 */
    if (tupdesc->attrs[2].atttypid != INT4OID)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("invalid return type"),
                errdetail("Third column must be type %s.", format_type_be(INT4OID))));

    /* check that the type of the fourth column is TEXT if applicable */
    if (show_branch && tupdesc->attrs[3].atttypid != TEXTOID)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("invalid return type"),
                errdetail("Fourth column must be type %s.", format_type_be(TEXTOID))));

    /* check that the type of the fifth column is INT4 */
    if (show_branch && show_serial && tupdesc->attrs[4].atttypid != INT4OID)
        elog(ERROR,
            "query-specified return tuple not valid for Connectby: "
            "fifth column must be type %s",
            format_type_be(INT4OID));

    /* check that the type of the fifth column is INT4 */
    if (!show_branch && show_serial && tupdesc->attrs[3].atttypid != INT4OID)
        elog(ERROR,
            "query-specified return tuple not valid for Connectby: "
            "fourth column must be type %s",
            format_type_be(INT4OID));

    /* OK, the tupdesc is valid for our purposes */
}

/*
 * Check if spi sql tupdesc and return tupdesc are compatible
 */
static bool compatConnectbyTupleDescs(TupleDesc ret_tupdesc, TupleDesc sql_tupdesc)
{
    Oid ret_atttypid;
    Oid sql_atttypid;

    /* check the key_fld types match */
    ret_atttypid = ret_tupdesc->attrs[0].atttypid;
    sql_atttypid = sql_tupdesc->attrs[0].atttypid;
    if (ret_atttypid != sql_atttypid)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("invalid return type"),
                errdetail("SQL key field datatype does "
                          "not match return key field datatype.")));

    /* check the parent_key_fld types match */
    ret_atttypid = ret_tupdesc->attrs[1].atttypid;
    sql_atttypid = sql_tupdesc->attrs[1].atttypid;
    if (ret_atttypid != sql_atttypid)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("invalid return type"),
                errdetail("SQL parent key field datatype does "
                          "not match return parent key field datatype.")));

    /* OK, the two tupdescs are compatible for our purposes */
    return true;
}

/*
 * Check if two tupdescs match in type of attributes
 */
static bool compatCrosstabTupleDescs(TupleDesc ret_tupdesc, TupleDesc sql_tupdesc)
{
    int i;
    Form_pg_attribute ret_attr;
    Oid ret_atttypid;
    Form_pg_attribute sql_attr;
    Oid sql_atttypid;

    if (ret_tupdesc->natts < 2 || sql_tupdesc->natts < 3)
        return false;

    /* check the rowid types match */
    ret_atttypid = ret_tupdesc->attrs[0].atttypid;
    sql_atttypid = sql_tupdesc->attrs[0].atttypid;
    if (ret_atttypid != sql_atttypid)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("invalid return type"),
                errdetail("SQL rowid datatype does not match "
                          "return rowid datatype.")));

    /*
     * - attribute [1] of the sql tuple is the category; no need to check it -
     * attribute [2] of the sql tuple should match attributes [1] to [natts]
     * of the return tuple
     */
    sql_attr = &sql_tupdesc->attrs[2];
    for (i = 1; i < ret_tupdesc->natts; i++) {
        ret_attr = &ret_tupdesc->attrs[i];

        if (ret_attr->atttypid != sql_attr->atttypid)
            return false;
    }

    /* OK, the two tupdescs are compatible for our purposes */
    return true;
}
